The Askania type micro-manometer and the liquid column manometer in which the liquid column height is measured visually have been commonly used as standard instruments to measure a micro-pressure or micro-differential pressure. A model in which a force that acts on the ram mechanism of a cylinder is weighed by an electronic weighing device has been also used.
Furthermore, a method in which the differential pressure is electrically detected by a strain gauge, a semiconductor gauge or the like is also used, but not widely.
However, for example, with the former, i.e., the Askania type micro-manometer in which the liquid column height is measured visually, the maximum resolution power of the measuring is approximately 0.01 mm. This means that it is totally impossible to continuously and accurately measure the micro-differential pressure of the water column of a nanometer (nmAq) order lower than 0.01 mm. And, the measured values cannot be outputted as electric signals continuously.
With the latter, i.e., the electronic differential pressure measuring device wherein an electronic weighing device is employed, the measurement result can be outputted as electric signals continuously. However, this device has a problem that the occurrence of measurement errors arising from the friction of moving or sliding parts and a low degree of mechanical machining precision is unavoidable because the device is so constituted that a force generated by the pressure to be measured is transmitted to an electronic weighing and pressure converting device by way of a stem, a ram and the like with the result that a high-precision measurement of the micro-differential pressure can not be achieved. (The JITSU-KOU-HEI No.6-76937 and the TOKU-KOU-HEI No.2-52975 and others)
The problem is shared by a wide-use type electronic differential pressure measuring device which is aimed to measure the differential pressure of approximately 2˜5 atmospheric pressure. Measurement errors due to friction of moving parts are also unavoidable, thus resulting in failure of the high-precision measurement.
Patent Literature 1 Public Bulletin JITSU-KOU-HEI No.6-76937
Patent Literature 2 Public Bulletin TOKU-KOU-HEI No.2-52975